a) Field of the Invention
The present invention relates to a network diagnostic device, a network diagnostic method, and a network system having diagnostic facility for the network.
b) Description of the Related Art
In a previously proposed diagnostic method for a network having a plurality of control units, each control unit being connected to a common communication line via a corresponding branch line, a communication malfunction indicative lamp installed for each control unit is illuminated to inform a user of an occurrence of the communication malfunction and, then, the user replaces the corresponding control unit on which the communication malfunction indicative lamp is illuminated with a new one so that the network is recovered to its original, normal communication state in a case where each control unit detects the occurrence of the malfunction of communications in itself, viz., within an internal of its control unit by means of its self-diagnostic function.
In the previously proposed diagnostic method for the network, in a case where the control unit itself has failed, the network system is recovered to its normal communication state with the failed control unit replaced with the new one.
However, in a case where a failure (or, so-called, a trouble) due to a broken line or due to a ground fault occurs in a certain point of place in the common communication line, the self-diagnostic function (facility) that each control unit has cannot identify the failed point of place (cannot locate the trouble) and the user must remove sequentially the related control units on each of which the communication failure indicative lamp is illuminated to identify the failed point of place, thereby lots of cost and time being required.
It is therefore an object of the present invention to provide a network diagnostic device, a network diagnostic method, and a network system having a diagnostic facility which can easily locate the trouble in communication even in the common communication line of the network in addition to the trouble in each branch line connected to its corresponding one of the plurality of control units when a communication malfunction in the network occurs.
The above-described object can be achieved by providing a network diagnostic device, comprising: a diagnostic communication line connected to all of a plurality of control units, each of the control units being connected to a common communication line via its corresponding branch line to enable a mutual communication with the other control unit; a normal state determining section that operatively performs such a network diagnostic processing as to cause each one of the control units to transmit an interrogation signal to all of the other control units and as to determine whether an acknowledgement signal is transmitted from each of the all of the other control units to the each one of the control units in response to the interrogation signal within a predetermined period of time to determine a normal state of a communication between each one of the control units and the other thereof; and a map display section that displays a correlation map in a matrix form having a plurality of matrix intersections, each matrix intersection being a one-to-one combination of any one of the control units and the other of the control units and being displayed in a pattern such as to be discriminated between the normal state of the communication and an abnormal state thereof.
The above-described object can also be achieved by providing a network diagnostic method, comprising: connecting a diagnostic communication line to all of a plurality of control units, each of the control units being connected to a common communication line via its corresponding branch line to enable a mutual communication with the other control unit; performing such a network diagnostic processing as to cause each one of the control units to transmit an interrogation signal to all of the other control units and as to determine whether an acknowledgement signal is transmitted from each of the all of the other control units to the each one of the control units in response to the interrogation signal within a predetermined period of time to determine a normal state of a communication between each one of the control units and the other thereof; and displaying a correlation map in a matrix form having a plurality of matrix intersections, each matrix intersection being a one-to-one combination of any one of the control units and the other of the control units and being displayed in a pattern such as to be discriminated between the normal state of the communication and an abnormal state thereof.
The above-described object can also be achieved by providing a network system having a network diagnostic facility, comprising: a plurality of control units, each one of the control units being connected to a common communication line via its corresponding branch line to enable a mutual communication with the other control unit; a normal state checking facility responsive to a diagnostic command signal from an external to the network system to transmit an interrogation signal from any one of the control units to all of the other control units which are connected to the common communication line and to output respective results of receiving acknowledgement signals from the all of the other control units within respective constant periods of time in response to the interrogation signal transmitted from the one of the control units to the external to the network system, the health state checking facility being installed on each of the control units.